Saw a truck around town today with a ridiculous lift kit and chunky off-road tires that were clearly much larger than factory standard, and it got me thinking; if you install this kind of modification in a car, do you need to adjust the speedometer to compensate? What about the odometer?
My logic is the only absolute measurement the car has is how fast the wheels and drive shaft are turning, so presumably there is some sort of multiplier - 1 revolution = X meters - that is then used to show speed and track distance travelled, but that factor would need to change if the circumference of the tires did
I have a vivid memory of staying home sick from school and watching daytime educational programming on PBS. There was a (dry, low-budget, old) math show for kids on. They had a “skit” where a couple of teenagers went and got replacement tires for their car. They came in with a set of numbers that I assume had to do with the tire measurements. (Maybe hub diameter, hub thickness, and tire outer diameter.) They found tires that matched on two of those numbers, but the guy was impatient and said it had to be basically the same because it matched on two parameters. Then in the next scene, the same teens were driving the car with brand new tires and they got pulled over for speeding. The driver was sure the speedometer said he wasn’t speeding, but the new outer tire diameter changed the calculation, meaning the speedometer read lower than they were actually going.
This is the first time in my life the memory of that show has ever come in handy.
I remember that show! Not that episode specifically.
If it’s the one I’m thinking of, it was called Square One.